Optical system

ABSTRACT

An optical system for simultaneously superimposing optical images from two separated object means on a single common line at the imaging point is disclosed. The system includes a fixed object lens and two plane reflecting means located equidistant from the lens center and the imaging plane, the reflecting means being mounted geometrically parallel to each other, optically parallel to the optic axis and equally spaced therefrom. The object means may be transparencies or opaque documents. The system may be utilized in a slit-scanning mode of operation or can be used to project and superimpose full frame images or areas in the imaging plane. The system may also be utilized to generate two identical images from a single original.

United States Patent [191 Wharton Sept. 18, 1973 OPTICAL SYSTEM [75]Inventor: Armistead Wharton, Henrietta, NY.

[73] Assignee: Xerox Corporation, Stamford, Conn.

[22] Filed: Dec. 13, 1971 [21] Appl. No.: 207,090

[52] US. Cl. 355/46, 355/50 [51] Int. Cl. G03b 27/44 [58] Field ofSearch 95/45; 355/33, 50, .355/46 [56] References Cited UNITED STATESPATENTS 3,254,579 6/1966 l-ligonnet 95/45 3,349,677 10/1967 Young 95/4.5

2,066,679 1 1/1937 'Fis'cherQ... 355/33 I 3,580,675 5/1971 Hieber et a1.355/50 3,584,950 6/1971 Gundlach 355/50 Primary Examiner-John M. l-loranAttorney-James J. Ralabate et al.

[57] ABSTRACT An optical system for simultaneously superimposing opticalimages from two separated object means on a single common line at theimaging'point is disclosed. The system includes a fixed object lens andtwo plane reflecting means located equidistant from the lens center andthe imaging plane, the reflecting means being mounted geometricallyparallel to each other, optically parallel to the optic axis and equallyspaced therefrom. The object means may be transparencies or opaquedocuments. The system may be utilized in a slitscanning mode ofoperation or can be used to project and superimpose full frame images orareas ,in vthe imaging plane. The system may also be utilized togenerate two identical images from a single Original;

- 7 Claims, 2 Drawing Figures INVENTOR. ARMISTEAD 'WHARTON BY p.

ATTORNEY OPTICAL SYSTEM BACKGROUND OF THE INVENTION This inventionrelates to an optical system for forming images and more specifically toan optical system capable of superimposing separate images on a commonline or area at the imaging point.

There are many applications wherein it is desired to superimpose imagesobtained from two separate originals on a common line or area atanimaging point. One such application is in .a photoelectrophoreticimaging system which is described in detail in US. Pats. Nos. 3,383,993;3,384,565 and 3,384,566. In photoelectrophoretic imaging, generallyspeaking, a layer of an imaging suspension comprising electricallyphotosensitive pigment particles in a carrier liquid is arranged betweentwo electrodes, one of which is at least partially transparent, exposedto an imagewise pattern of activating electromagnetic radiationcorrespondint to an plete image is reproduced.I-Iowever this usuallyresults in a dark or colored border being formed .around the reproducedimage whichwis undesirableqin a'commercial imaging system. Thus it wouldbe desirable to be able to project a white border simultaneously withthe projection of the original image on the suspension layer.

Previously known schemes for accomplishing superimposition of images ata common imaging point have typically utilized beamsplitters. Howeverbeam splitter arrangements, as is well known, typically work at lessthan 50 percent efficienty. Thus to obtain a desired level ofillumination at the imaging plane roughly twice that desiredilluminancemust be provided to illuminate the original image. In acommercial imaging systeman optical arrangement which operates at lessthan 50 percent efficiency would require considerably higher powerlevels toprovide the necessary illuminance at the imaging point. Thistype of an arrangement would obviously behighlydisadvantageous from aneconomical viewpoint. Furthermore, cooling of the equipment in such anarrangement could become a troublesome problem, necessitating additionalapparatus and thereby undesirably complicating the overall device Iconfiguration. Thus in'an instance such as that described aboye it wouldbe desirable to have a method for superimposing optical images whichoperates at substantially full optical light efficiency.

SUMMARY OF THE INVENTION .from two separated original images on a singlecommon line at an imaging point.

It is a further object of the invention to provide such a system whichoperatesat substantially full optical light efficiency.

It is still another object of the invention to provide such an opticalsystem wherein both separated original images may be mounted in a singlescanning carriage.

Yet another object of the invention is to provide such an optical systemwhich may be used for full frame projection and superimposition withoutscanning.

It is a still further object of the invention to provide an opticalsystem which may be utilized to generate two identical separated imagesfrom a single original.

These and other objects and advantages are accomplished in-accordancewith the invention by providing an optical system in which a singlefixed lens is capable of projecting and superimposing images from twoseparated original objects on a single common line or area at theimaging plane. The single fixed lens views and projects the illuminatedoriginal images to two plane reflecting means located equidistant fromthe lens center and the imaging plane. The plane reflecting means aremounted plane parallel to each other, optically parallel to the opticalaxis and equally spaced therefrom.

The projected images strike the reflecting means and are reversed anddirected to the final imaging point or area where they are superimposedon each other.

The novel optical system of the'invention may be utilized in aslit-scanning mode of operation or in a full frame projection modewithout scanning. The original objectsmay be transparencies or they maybe opaque documents.

Except for minor mirror losses the optical system "of the inventionoperates at substantially full optical light efficiency in contrast withbeam splitter arrangements which usually work at less than 50 percentefficiency. The system also offersthe advantage that both originalimages can be mounted in the same carriage.

The invention will be more fully understood from the following detaileddescription of various preferred embodiments thereof particularly whenread in conjunction with the accompanying drawings wherein:

FIG. 1 is a partially schematic cross-sectional view illustrating apreferred embodiment of theinvention; and

FIG. 2 is a partially schematic cross-sectional view illustratinganother preferred embodiment ofthe invention.

Referring now to FIG. lthere is seen a scanning carriage 10 positionedat the film plane 111 and which moves in the direction indicated by thearrow. The scanning carriage is capable of carrying at least twoseparated original objects; original objects 112 and 14 areshown for thepurpose of illustration. The original images which can be superimposedat a common point according to the optical system of the invention aretypically provided in the form of transparencies and, in a preferredinstance, may be a 35 mm original slide and a border generating slide.Although the invention is described, in this illustrative instance, withrespect to the slit-scanning mode of operation it should be recognizedthat it may be employed for full frame projection without scanning.Adjacent toscanning carriage is located a fixed slit mask, generallydesignated 16, having slits 118. and 24). Original objects 12 and 14 arepositioned in the scanning carriage so as to arrive simultaneously atslits l8 and 20 respectively. As the scanning carriage transports theoriginal objects 12 and 14 past slits 18 and 20 respectively, theobjects are illuminated by means of light sources 21 located behind thescanning carriage.

Although the invention is being described in detail with respect to thesuperimposition of images or original objects which are in the form oftransparencies it will, of course, be obvious to those skilled in theart that when the system is utilized to operate with opaque documentsthe light sources 21 will be positioned on the opposite side of theimaging position from that shown.

The illuminated objects at slits l8 and 20 are viewed by fixedprojection lens 22. Projection lens 22 typically has a wide enough fieldto pick up light from both of the illuminated objects 12 and 14. Thefixed lens 22 projects images of the illuminated objects to two flatmirrors 24 and 26 located equidistant from the lens center and theimaging plane 28. Mirrors 24 and 26 are preferably first surface mirrorshaving reflecting surfaces 24' and 26' respectively and are mountedplane parallel to each other, parallel to the optic axis 30 and equallyspaced therefrom. First surface mirrors, i.e., those having a reflectingcoating on one of the glass surfaces which is usually a vacuum depositedaluminum film protected by a thin transparent overcoating of siliconmonoxide, are typically necessary to prevent ghost images from beingformed at the imaging plane. The mirrors 24 and 26 reverse the sense ofthe projected images from slits '18 and 20 respectively and direct theprojected images to the final imaging points 31 at the imaging plane. Ofcourse any light reflecting materials such as, for example, prisms maybe used according to the invention. Positioned between mirrors 24 and 26is optional light baffle 32 which is preferably arranged to prevent anyundesired light from reaching the imaging plane.

The projected images are directed through slit 34 of fixed imaging'slitmask 36 and are superimposed at the final imaging area 31 on the imagereceiving member 35 which is located at the imaging plane 28. The imagereceiving member 35 may be any of many different materials such as, forexample, a photoconductive insulating surface, a photographic film, atraveling web, etc. Of course where the scanning mode of operation ispracticed and the scanning carriage moves in the direction of the arrow,the image receiving member 35 will also be moved in the direction of thearrow. Alternatively the scanning mode of operation may also bepracticed by holding the scanning carriage 10 and image receiving member35 fixed and moving the other elements of the apparatus with relation tothem.

Any desired magnification can be obtained by adjusting the spacing ofthe various elements of the optical system. The following discussionconcerning the arrangement of the elements of the system will beillustrative.

Let y designate the spacing between the two original transparencies atthe viewing slits 18 and 20. Then by geometric triangulation, thespacing between the pro-- jected real images 40 and 42 will be MY whereM is the magnification ratio. Also by geometry, thespacing between thetwo mirrors 24 and 26 will be MY/2. Using the common lens formulae, therelations between'object distance, image distance, focal length andmagnification can be readily established as follows: if X represents theobject distance, then MX will be the image distance and l/X l/MX 1/Fwhere F is the focal length of the lens. Then F (MX/M l) X F(M l)/M andMX F(M+l) so that one variable can be determined if the other twovariables are known. It is seen that both of the images projected byfixedlens 22 ofX and Y since a tan Y/2.

The optical system of the present invention can operate at variousmagnifications as has been seen. However the system becomes large andunwiedly as the ratio of the conjugates becomes larger. In a preferredembodiment of the invention wherein the novel optical system is employedto produce enlarged reproductions from relatively small (e.g., 35 mm)transparencies it is particularly preferred to use magnifications in thegeneral range of 1:2 to 1:8. Where the optical system is used toreproduce opaque originals a magnification ratio of 1:1 will usually bepreferred. For example, document copying equipment, either of thescanning type or the full frame exposure type typically requires thecopy to be about the same size as the original. Of course it will berecognized that the optical system may be used in a demagnification modewhere it is desired to form optical images at the imaging point whichare smaller than the original objects sought to be superimposed.

It will be further appreciated by those skilled in the art that when theslit scanning mode of operation is practiced with a moving scanningcarriage and a moving optical image receiving member and the system isarranged for a 1:1 magnification ratio, the scanning carriage and theoptical image receiving member will typically be moved in the samedirection at the same speed. If the same mode of operation is practicedwith a difierent magnification ratio then the optical image receivingmember will typically be moved at a different ratio of speed relative tothe scanning carriage corresponding to the particular magnificationratio used. For example if a magnification ratio of about 3:1 is usedthe optical image receiving member will typically be moved at a rate ofspeed about three times faster than the rate of speed at .which thescanning carriage is moved.

FIG. 2 illustrates the practice of the invention in the full frameprojection mode. The apparatus shown in FIG. 2 is similar to that shownin FIG. 1 with like elements being designated with like numerals. Inthis mode of operation the object carriage and the image receivingmember are stationary. It will be noted that slits 18 and 20' of fixedslit mask 16 and slit 34 of fixed imaging slit mask 36 are larger thanthe corresponding slits in FIG. 1.

Although the optical system has been described with respect to apreferred embodiment of the invention wherein the novel optical systemis advantageously utilized to'superimpose projected images from twoseparated original images it should be recognized that it may also beused to generate two identical separated images from a single originalobject. According to this embodiment of the invention the apparatusconfiguration is identical with that shown in FIG. 1 and FIG. 2 with theexception that the object plane and the imaging plane are reversed. inother words the object plane shown in the drawings becomes the imagingplane and the imaging plane becomes the object plane. Of course thelight sources must be positioned behind the original object at the filmplane.

,While the novel optical system has been described in detail withrespect to simultaneous superimposition of transparencies it will bereadily apparent that the invention is not limited to this embodiment.Images of illuminated opaque documents may be projected and superimposedusing the same optical elements and arrangements and this may beaccomplished in either the moving, slit-scanning mode or, preferably,the fixed full-frame mode. It will also be apparent that a furthercapability of the novel optical system resides in the superimposition ofimages from an illuminated opaque document and an illuminatedtransparency.

There has been described an efficient and highly advantageous opticalsystem. While the invention has been illustrated relative to particularpreferred embodiments thereof it is not intended to be limited theretobut rather it will be appreciated by those skilled in the art thatmodifications and variations are possible which are within the spirit ofhe invention and the scope of the claims.

What is claimed is:

1. An optical apparatus including the following disposed along anoptical axis:

a. a projection lens disposed between conjugate object and image planes,

b. a mask disposed adjacent said object plane and defining a pluralityof apertures all spaced equidistant from said optical axis for thepropagation, through each of said apertures, of light from said objectplane along projection axes extending from said apertures through saidprojection lens to said image plane,

c. a reflecting surface, facing said optical axis an spaced therefrom,disposed in each projection axis so that the point of incidence of saidprojection axis on said reflecting surface is midway between saidprojection lens and said image plane, and

d. a movable object carriage to move objects in saidobject plane and toposition said objects in registry with said apertures,

whereby light rays propagating from said object plane through saidapertures form images at said image plane in upright and overlappingposition and an image receiving means located at said image plane andarranged for movement in the same direction as that of said objectcarriage.

2. The apparatus as defined in claim 1 wherein the magnification ratiois from about 1:2 to about 1:8.

3. The apparatus as defined in claim 1 wherein the magnification ratiois about 1:1.

4. An optical apparatus as defined in claim 1 wherein said reflectingsurfaces and said apertures are equal in number,

said reflecting surfaces being disposed in an array symmetrical to thatof said apertures with respect to said optical axis.

5. An optical apparatus as defined in claim 1 in which said objectdistance is a value X, said image distance is MX (where M equals thelateral magnification of the system), said apertures are spaced apart ontheir centers by a value Y, and said reflecting surfaces arecorrespondingly spaced apart by a value MY/2.

6. An optical apparatus as defined in claim 1 in which said objectcarriage includes means to sequentially introduce combinations ofobjects in registry with said apertures.

7. An optical apparatus as defined in claim 1 in which said aperturesand mirrors are two in number and said object carriage is effective tosequentially introduce pairs of objects in simultaneous registry withsaid aper-

1. An optical apparatus including the following disposed aloNg anoptical axis: a. a projection lens disposed between conjugate object andimage planes, b. a mask disposed adjacent said object plane and defininga plurality of apertures all spaced equidistant from said optical axisfor the propagation, through each of said apertures, of light from saidobject plane along projection axes extending from said apertures throughsaid projection lens to said image plane, c. a reflecting surface,facing said optical axis and spaced therefrom, disposed in eachprojection axis so that the point of incidence of said projection axison said reflecting surface is midway between said projection lens andsaid image plane, and d. a movable object carriage to move objects insaid object plane and to position said objects in registry with saidapertures, whereby light rays propagating from said object plane throughsaid apertures form images at said image plane in upright andoverlapping position and an image receiving means located at said imageplane and arranged for movement in the same direction as that of saidobject carriage.
 2. The apparatus as defined in claim 1 wherein themagnification ratio is from about 1:2 to about 1:8.
 3. The apparatus asdefined in claim 1 wherein the magnification ratio is about 1:1.
 4. Anoptical apparatus as defined in claim 1 wherein said reflecting surfacesand said apertures are equal in number, said reflecting surfaces beingdisposed in an array symmetrical to that of said apertures with respectto said optical axis.
 5. An optical apparatus as defined in claim 1 inwhich said object distance is a value X, said image distance is MX(where M equals the lateral magnification of the system), said aperturesare spaced apart on their centers by a value Y, and said reflectingsurfaces are correspondingly spaced apart by a value MY/2.
 6. An opticalapparatus as defined in claim 1 in which said object carriage includesmeans to sequentially introduce combinations of objects in registry withsaid apertures.
 7. An optical apparatus as defined in claim 1 in whichsaid apertures and mirrors are two in number and said object carriage iseffective to sequentially introduce pairs of objects in simultaneousregistry with said apertures.